The Basilica of St. Peter is one of four Papal Basilicas or Major Basilicas of Rome. It is the most prominent building in the Vatican City. Its dome is a dominant feature of the skyline of Rome. Probably the largest church in Christendom, it covers an area of 2.3 hectares (5.7 acres). One of the holiest sites of Christianity in the Catholic Tradition, it is traditionally the burial site of its titular Saint Peter, who was one of the twelve apostles of Jesus and, according to Catholic Tradition, also the first Bishop of Antioch and later first Bishop of Rome, the first Pope. Although the New Testament does not mention Peter's martyrdom in Rome, Catholic tradition holds that his tomb is below the baldachin and altar; for this reason, many Popes have, from the early years of the Church, been buried there. Construction of the current basilica, over the old Constantinian basilica, began on 18 April 1506. On 18 November 1626, Pope Urban VIII solemnly dedicated the church.